1. Field of the Invention
The present invention relates to a manufacturing method of a plugged honeycomb structure. Particularly, it relates to a manufacturing method of a plugged honeycomb structure in which the plugged honeycomb structure having reduced deposits deposited on an end surface thereof when used as a filter or the like can easily be manufactured with low cost. More particularly, it relates to a manufacturing method of a plugged honeycomb structure in which a plugging depth of a honeycomb structure can easily be set to be uniform.
2. Description of the Related Art
In recent years, in various fields of chemistry, electric power, iron and steel and industrial waste disposal, a plugged honeycomb structure made of a ceramic having excellent resistances to heat and corrosion is used as a filter for dust collection to be used in applications including an environmental countermeasure such as pollution prevention, and recovery of a product from a high-temperature gas. For example, such a plugged honeycomb structure is preferably used as the filter for dust collection to be used in a corrosive gas atmosphere at a high temperature, for example, a diesel particulate filter (DPF) which traps particulates to be discharged from a diesel engine (e.g., Patent Document 1).
As shown in FIG. 5, a plugged honeycomb structure for use as the above filter for dust collection includes a cylindrical honeycomb structure 23 having porous partition walls 22 by which a plurality of cells 24 are separated from one another to constitute channels of a fluid, and plugging members 26 which plug openings of predetermined cells on one side of the structure and which plug openings of remaining cells on the other side of the structure. In a plugged honeycomb structure 21 shown in FIG. 5, inlet-side end surfaces B and outlet-side end surfaces C of the plurality of cells 24 are alternately in a checkered pattern plugged by the plugging members 26.
The above plugged honeycomb structure 21 can be manufactured by obtaining a cylindrical non-fired honeycomb structure having porous partition walls by which the plurality of cells are separated from one another to constitute the channels of the fluid by extrusion forming. Subsequently, the openings of the predetermined cells on one side and the openings of the remaining cells on the other side of the resultant non-fired honeycomb structure or the honeycomb structure obtained by firing the non-fired honeycomb structure are filled with a plugging slurry including a ceramic. Afterward, the structure is fired.
Furthermore, as a manufacturing method of the plugged honeycomb structure for use as the above filter for dust collection, a method is proposed in which, for example, an adhesive sheet or the like is attached to one end surface of a formed honeycomb body as a non-fired ceramic dry body, and holes are made at portions of the adhesive sheet or the like corresponding to the cells to be plugged (plugged cells) by laser processing or the like by use of image processing. The end surface of the formed honeycomb body to which the adhesive sheet or the like is attached as a mask is submerged into a slurry (a ceramic slurry). The plugged cells of the formed honeycomb body are filled with the slurry to form the plugging portions. The other end surface of the formed honeycomb body is subjected to a step similar to the above step. Subsequently, the body is dried and fired to thereby obtain the plugged honeycomb structure (e.g., Patent Document 1).
Patent Document 1: Japanese Patent Application Laid-Open No. 2001-300922
Patent Document 2: Japanese Patent Application Laid-Open No. 2005-270755
In the above manufacturing method of the plugged honeycomb structure, to set depths of the plugging portions to be uniform, it is demanded that the openings be uniformly plugged with a slurry-like plugging member including the ceramic slurry. Therefore, a liquid surface of the slurry-like plugging member in a container in which the slurry-like plugging member including the ceramic slurry is stored needs to be leveled. However, even in a step of leveling the liquid surface of the slurry-like plugging member, the slurry-like plugging member escapes toward a side surface of the honeycomb structure at an outer peripheral portion of the honeycomb structure. Therefore, a problem that the penetration depth of the plugging portion obtained by the slurry-like plugging member at the outer peripheral portion of the honeycomb structure often becomes insufficient remains unsolved.